This invention concerns a soundproofed conduit to discharge fumes.
The invention is applied in particular, but not exclusively, in the field of steel production in order to soundproof the delivery side of the fans connected to the outlet chimneys, associated with the melting systems, such as electric furnaces and similar, through which the fumes are discharged to the environment.
The state of the art covers conduits to discharge fumes, usually made of brickwork and metallic structural work, through which the fumes generated by the melting systems, such as for example electric furnaces, after being passed through the opportune filter systems, are discharged into the environment.
The fumes are directed to the discharge conduits by means of the appropriate ventilation and conveying systems, which cooperate with conduits to deliver the fumes to the chimney.
It is well-known that a great deal of noise is caused as the fumes are conveyed by these ventilation systems; to obviate this problem, soundproofing systems are normally included and associated with the discharge conduits.
In the field of steel production, the inner part of the discharge conduits are normally at least partly lined with sound absorbent panels made with a plurality of adjacent baffles made of mineral wool or a similar material.
The traditional structure of such discharge conduits such as are known to the state of the art is shown in FIG. 7. It includes ventilation systems 22 connected by means of structural connections 26 to soundproofing elements 23 structured in soundproofing packs or panels which are in turn connected, by means of connection means 24, to the chimney 25.
However, these sound absorbent panels or packs are subject to premature wear and have the disadvantage that, with time, they release into the environment fibres, dust or particles of various grain size, which causes a further and often considerable secondary pollution.
Moreover, as the layer releases particles into the environment, it becomes progressively thinner as a result, and therefore the capacity of the panel to absorb sound is reduced.
This situation requires frequent maintenance operations, both to maintain the soundproofing effect of the sound absorbent panels and also to prevent the spread of polluting substances into the environment.
The sound absorbent panels moreover are very expensive, difficult and troublesome to install and require both specialised personnel and long installation times.
This leads to considerable increases in running costs, long and frequent downtimes of the plant, difficulties in finding the specialised staff to install the panels, and still other disadvantages.
Such structural connections which are normally included in conduits known to the state of the art are, moreover, subject to premature wear and require continuous and constant maintenance.
In physics there is also the concept whereby the angular diversion of a transit conduit for fluids causes a reduction in the noise created by the passage of the said fluid.
This concept, connected with the reduction of noise, has been used so far, in the field of steel production, for air conditioning conduits (for example in U.S. Pat. No. 4,395,023, FIGS. 10 and 11) but never for discharge conduits of the chimney type made of brickwork. Moreover, solutions have been proposed which use elbow-shaped curved conduits in order to discharge the fluids, but with regard to problems of a completely different nature and with normal conduits with connected curved segments.
For example, GB-A-1.154.335 describes a system to control the fluctuations in pressure of gases emitted from a melting container so that the pressure can be controlled in the gas recovery system.
In order to control this pressure, GB'335 includes a plurality of breather pipes arranged on a chimney located above the melting container so that the pressure is controlled without being influenced by pulsations which derive from abrupt variations in the reactions inside the container.
The conduit to discharge the fumes is shaped with connected curved segments, but this is quite random and justified by structural, not functional reasons.
GB-A-1.348.075 includes a system of movable pipes to discharge the fumes produced by an oscillating melting container; the pipes are coupled to each other with flanges which rotate with respect to each other so that the whole system of pipes can follow and adapt to the movements of the container for melting the metal.
In this case too, the arrangement of the pipes in connected curved segments is purely random and does not concern the chimney.
U.S. Pat. No. 2,268,918 also provides substantially a flexible connection between the chimney and the discharge system so as to follow the oscillatory movements of the melting container during the pouring of the liquid metal.
These three prior art documents are not concerned with the problems connected to the reduction of noise in discharge conduits of the chimney type made of brickwork.